feat(Go-Tool)：2020/11/12:新增linq包使用示例(未完成)

2020-11-12 18:10:15 +08:00
parent 3616c4b5e5
commit 2ac2b2666f
33 changed files with 2517 additions and 0 deletions
@@ -0,0 +1,141 @@
+# go-linq [![GoDoc](https://godoc.org/github.com/ahmetalpbalkan/go-linq?status.svg)](https://godoc.org/github.com/ahmetalpbalkan/go-linq) [![Build Status](https://travis-ci.org/ahmetalpbalkan/go-linq.svg?branch=master)](https://travis-ci.org/ahmetalpbalkan/go-linq) [![Coverage Status](https://coveralls.io/repos/github/ahmetalpbalkan/go-linq/badge.svg?branch=master)](https://coveralls.io/github/ahmetalpbalkan/go-linq?branch=master) [![Go Report Card](https://goreportcard.com/badge/github.com/ahmetalpbalkan/go-linq)](https://goreportcard.com/report/github.com/ahmetalpbalkan/go-linq)
+A powerful language integrated query (LINQ) library for Go.
+* Written in vanilla Go!
+* Safe for concurrent use
+* Complete lazy evaluation with iterator pattern
+* Supports arrays, slices, maps, strings, channels and custom collections
+(collection needs to implement `Iterable` interface and element - `Comparable`
+interface)
+
+## Installation
+
+    $ go get github.com/ahmetalpbalkan/go-linq
+
+> :warning: :warning: `go-linq` has recently introduced _breaking API changes_
+> with v2.0.0. See [release notes](#release-notes) for details. v2.0.0 comes with
+> a refined interface, dramatically increased performance and memory efficiency,
+> and new features such as lazy evaluation ([read more](http://kalan.rocks/2016/07/16/manipulating-data-with-iterators-in-go/)).
+>
+> The old version is still available in `archive/0.9` branch and tagged as `0.9`
+> as well. If you are using `go-linq`, please vendor a copy of it in your
+> source tree to avoid getting broken by upstream changes.
+
+## Quickstart
+
+Usage is as easy as chaining methods like:
+
+`From(slice)` `.Where(predicate)` `.Select(selector)` `.Union(data)` 
+
+**Example: Find all owners of cars manufactured from 2015**
+```go
+import . "github.com/ahmetalpbalkan/go-linq"
+	
+type Car struct {
+    id, year int
+    owner, model string
+}
+
+owners := []string{}
+
+From(cars).Where(func(c interface{}) bool {
+	return c.(Car).year >= 2015
+}).Select(func(c interface{}) interface{} {
+	return c.(Car).owner
+}).ToSlice(&owners)
+```
+
+**Example: Find the author who has written the most books**
+```go
+import . "github.com/ahmetalpbalkan/go-linq"
+	
+type Book struct {
+	id      int
+	title   string
+	authors []string
+}
+
+author := From(books).SelectMany( // make a flat array of authors
+	func(book interface{}) Query {
+		return From(book.(Book).authors)
+	}).GroupBy( // group by author
+	func(author interface{}) interface{} {
+		return author // author as key
+	}, func(author interface{}) interface{} {
+		return author // author as value
+	}).OrderByDescending( // sort groups by its length
+	func(group interface{}) interface{} {
+		return len(group.(Group).Group)
+	}).Select( // get authors out of groups
+	func(group interface{}) interface{} {
+		return group.(Group).Key
+	}).First() // take the first author
+```
+
+**Example: Implement a custom method that leaves only values greater than the specified threshold**
+```go
+type MyQuery Query
+
+func (q MyQuery) GreaterThan(threshold int) Query {
+	return Query{
+		Iterate: func() Iterator {
+			next := q.Iterate()
+
+			return func() (item interface{}, ok bool) {
+				for item, ok = next(); ok; item, ok = next() {
+					if item.(int) > threshold {
+						return
+					}
+				}
+
+				return
+			}
+		},
+	}
+}
+
+result := MyQuery(Range(1,10)).GreaterThan(5).Results()
+```
+
+**More examples** can be found in [documentation](https://godoc.org/github.com/ahmetalpbalkan/go-linq).
+
+## Release Notes
+~~~
+
+v2.0.0 (2016-09-02)
+* IMPORTANT: This release is a BREAKING CHANGE. The old version
+  is archived at the 'archive/0.9' branch or the 0.9 tags.
+* A COMPLETE REWRITE of go-linq with better performance and memory
+  efficiency. (thanks @kalaninja!)
+* API has significantly changed. Most notably:
+  - linq.T removed in favor of interface{}
+  - library methods no longer return errors 
+  - PLINQ removed for now (see channels support)
+  - support for channels, custom collections and comparables
+
+v0.9-rc4
+* GroupBy()
+
+v0.9-rc3.2
+* bugfix: All() iterating over values instead of indices
+
+v0.9-rc3.1
+* bugfix: modifying result slice affects subsequent query methods
+
+v0.9-rc3
+* removed FirstOrNil, LastOrNil, ElementAtOrNil methods 
+
+v0.9-rc2.5
+* slice-accepting methods accept slices of any type with reflections
+
+v0.9-rc2
+* parallel linq (plinq) implemented
+* Queryable separated into Query & ParallelQuery
+* fixed early termination for All
+
+v0.9-rc1
+* many linq methods are implemented
+* methods have error handling support
+* type assertion limitations are unresolved
+* travis-ci.org build integrated
+* open sourced on github, master & dev branches
+~~~